Soak vermicelli in warm water (immerse completely) for 30 minutes. Drain well and cut into 0.5cm pieces.
50 g of rice vermicelli (or mung bean noodles)
Rehydrate the black mushrooms and take 30g (and slice them), freeze the rest
30 g of black mushrooms
In a large bowl, mix the vermicelli, minced pork, grated carrot, black mushrooms, shallots, garlic, egg white, ginger, fish sauce, vegetable oil, salt, white pepper and 1 teaspoon of sugar. Mix until everything is evenly combined.
450 g of pork, 190 g of carrots, 30 g of shallots, 1 clove of garlic, 1 teaspoon of ginger, 1 egg white, 1 tablespoon of fish sauce, 1 tablespoon neutral vegetable oil, 0.5 teaspoon salt, 1 pinch white pepper, 1 teaspoon of sugar
To fold the egg rolls
In a large shallow bowl or deep plate, dissolve the remaining teaspoons of sugar in warm water. The sugar is optional but will help the spring rolls brown during cooking.
2 teaspoons of sugar, 250 ml warm water
To wrap each roll, place a sheet of rice paper in the sugar water for about 5 to 10 seconds, making sure it's completely submerged. Remove it from the water. It will still be quite firm, but it will soften quickly!
20 dried rice leaves (bánh tráng)
Place around 40 g of log-shaped filling on one side of the dough. Start folding the wrapper firmly over the filling (no air bubbles!) and roll the nem forward one full turn. Press lightly on each end of the filling to flatten the rice paper, and push the filling together to eliminate any air bubbles.
Fold one side of the wrapping towards the middle of the spring roll. Repeat with the other side. Roll the spring roll forward, tucking it in at the front to avoid air pockets. The rice paper will stick to itself. Nothing more is needed to seal them. Place the rolls on a plate or tray lined with a clean, dry kitchen towel or parchment paper.
Cooling
Once wrapped, transfer the egg rolls to the refrigerator and chill for at least 1 hour, to allow them to dry and firm up. This step helps to minimize bubbling of the packaging during frying (although slight bubbling is normal). Take them out of the fridge 15 minutes before frying.
Cooking egg rolls
Arrange the spring rolls in a single layer at the bottom of the Air Fryer basket
Lightly brush with oil (optional)
Cook for 10 minutes at 195 C (380F) degrees in Air Fryer mode, opening and shaking halfway through cooking
Notes
The recipe calls for 20 spring rolls, so I count about 2 rolls per person. You will have about 800 g of filling in total, so each of your 20 spring rolls should have about 40 g of filling. Thanks to Andre Souppaya, member of the site's official Facebook group, for the ultra-fast egg roll folding technique video.